Dual clumped isotope thermometry of carbonates: resolving the effects of temperature from kinetics and diagenesis for accurate reconstruction of Earth’s surface temperature

我们的星球是如何变得宜居的，为什么变得宜居？哪些边界条件触发了地球上生命的进化？气候将如何演变，它将如何影响生物多样性？为了找到这些重要问题的答案，必须重建过去大气温室气体丰度、地球表面温度和生物多样性之间的相互作用。地球表面温度是根据准确年代的沉积档案中的化学和同位素替代数据重建的。然而，目前还没有可以明确记录地球表面温度的指标。除了温度外，动力学和成岩作用以及母流体的化学和同位素组成也对沉积档案的替代成分起着控制作用。非排他性的温度控制和原始替代成分的二次改变在重建的温度中引入了很大的不确定性。我的研究小组最近开创了碳酸盐的双簇同位素分析，即对二氧化碳中稀有分子12C18O18O(Δ48)的丰度进行了极具挑战性的分析，这是碳酸盐与13C18O16O(Δ47)一起由磷酸消化而形成的。现在，双束同位素测温法首次允许我们仅通过分析单个碳酸盐相来解析动力学和成岩信息，而不需要进一步了解碳酸盐结晶所来自的流体的组成。它有可能成为重建准确的地层温度(不受动力学影响)的首选方法，具有前所未有的精度(在95%的可信区间水平上为±2℃)。我请求提供资金，以系统和全面地研究Δ47与Δ48空间中碳酸盐(生物)成矿的基本热力学和动力学系统。这可能使我们能够可靠地重建过去高二氧化碳时段地球表面温度和温室气体丰度之间的相互作用。要改进预测未来气候的最新模型，有必要提供准确的古纬度温度梯度，用于预测在不久的将来将遇到的二氧化碳含量高的纪元。此外，对基本热力学和动力学的探索将为双团簇同位素替代物的进一步潜在应用提供必要的信息。这些研究包括岩石埋藏和抬升的温度-时间路径的重建、海洋生物生产的演化、碳酸盐生物矿化对人为二氧化碳强迫的响应以及太古代以来地球表面温度和宜居性的演化。

How and why did our planet become habitable? Which boundary conditions triggered the evolution of life on Earth? How will climate evolve and how will it affect biodiversity? To find answers for these important questions it is essential to reconstruct the past interplay between atmospheric greenhouse gas abundances, Earth’s surface temperatures and biodiversity. Earth’s surface temperatures are reconstructed from chemical and isotopic proxy data from well-dated sedimentary archives. Yet, there is no proxy available that unambiguously records Earth’s surface temperature. Besides temperature, kinetic and diagenetic processes as well as the chemical and isotopic composition of the parent fluid exert control on the proxy composition of the sedimentary archive. Non-exclusive temperature control and secondary alteration of the original proxy composition introduce large uncertainties in reconstructed temperatures.My research group has most recently pioneered dual clumped isotope analysis of carbonates, i.e., the extremely challenging analysis of the abundance of rare molecules of 12C18O18O (Δ48) in CO2 evolved from phosphoric acid digestion of carbonates along with 13C18O16O (Δ47). Now, for the first time, dual clumped isotope thermometry, may allow us to resolve temperature from the kinetic and diagenetic information just from the analysis of a single carbonate phase, without requiring any further knowledge about the composition of the fluid from which the carbonate crystallized. It has the potential to become the method of choice for the reconstruction of accurate formation temperatures (unbiased by kinetics) with unprecedented precision (< ±2°C on the 95% confidence interval level).I request funding to systematically und comprehensively investigate the fundamental thermodynamic and kinetic systematics of carbonate (bio)mineralization in Δ47 vs. Δ48 space. This may allow us to reliably reconstruct the interplay between Earth’s surface temperature and greenhouse gas abundance for past high-pCO2 intervals. The provision of accurate paleo-latitudinal temperature gradients for epochs with pCO2 as high as predicted to be encountered in the near future is necessary to improve state-of-the-art models predicting future climate. Moreover, the exploration of fundamental thermodynamics and kinetics will provide information essential for further potential applications of the dual clumped isotope proxy. These include reconstructions of temperature-time paths of burial and uplift of rocks, the evolution of marine biological production, the response of carbonate biomineralization to anthropogenic CO2 forcing and the evolution of Earth’s surface temperature and habitability since the Archean.